Light Weight Directory Access Protocol (LDAP) has become very popular due to its efficient and fast data access. A large number of applications/services are currently being developed which use an LDAP directory as their centralized data repository.
The LDAP directory stores entries as a tree. Each entry may consist of one or more attribute names and attribute values. An entry may be uniquely identified by its distinguished name (DN) that may include a common name (cn) attribute of the entry and DN of a parent entry.
The contents of the entries are governed by an LDAP directory schema. The schema defines object classes, and each entry has an objectClass attribute containing named classes defined in the schema. The objectClass attribute may be multivalued, and contain the class “top” as well as some number of other classes. The schema definition for each class that an entry belongs to defines what kind of object the entry may represent (e.g., a person, organization or domain). Membership in a particular class gives the entry the option of containing one set of attributes (optional attributes), and the obligation of containing another set of attributes (mandatory or required attributes). For example, an entry representing a person might belong to the class “person”. Membership in the “person” class would require the entry to contain the “sn” and “cn” attributes, and allow the entry also to contain “userPassword”, “telephoneNumber”, and other attributes.
An LDAP directory server includes one or more access control mechanisms. Access control mechanisms evaluate requests for access to protected resources and make decisions about whether those requests should be granted or denied. In order to make a decision on whether to grant or to deny a request for access to a protected resource, an access control mechanism examines policy data that is stored in the form of access control information (ACI). The access control information describes security-relevant characteristics of the requesting subject and the rules which govern the use of the target object.